In recent years, systems for surgical simulations have become increasingly more used, in order to train physicians various surgical procedures without putting live patients at risk. In particular in the field of minimally-invasive surgery, such as laparoscopy, endoscopy, colonoscopy, etc., such simulation systems have gained significant acceptance. During minimal-invasive surgery the physician typically relies on an image on a screen rather than on an actual view of the patient, and with powerful image rendering available today, such an image can be simulated with a very high degree of realism.
In order to interact with the simulation software, the simulation system further requires an input device, i.e. hardware which the physician may operate and which simulates an actual surgical instrument. Such input devices should in physical appearance and function resemble an actual instrument. However, they must also provide sensor for detecting the current position of the simulated instrument, thereby enabling the simulation software to provide an appropriate image on the screen. In addition, such devices preferably include haptic feedback, i.e. provide feedback of forces that would be encountered during an actual procedure.
In the case of laparoscopy, an example of an input device is the Virtual Laparoscopic Interface (VLI) from Immersion Corp. This device includes a rigid shaft, corresponding to the instrument portion to be inserted into a patient, and a handle, with which the physician can move the instrument. In order to simulate the degrees of freedom of an actual instrument, which passes into a patient body through a small opening, the shaft is supported by a frame in a pivoting point with two degrees of freedom (rotation α, β). In addition, the shaft can be translated in linear motion along its longitudinal axis, i.e. in and out of a simulated body, as well as rotated around this longitudinal axis. The handle further includes a grip portion, allowing the physician to operate a simulated surgical tool at the tip of the instrument. The input device contains sensors for all degrees of freedom including rotation of the shaft. Most sensors are provided in vicinity of the pivoting point, except the sensor of grip action, which is detected in the handle and provided through a separate signal interface on the handle. This signal interface is thus movable in relation to the frame, and connected to the frame with a cord. Just as in an actual instrument, the grip portion may further be rotated in relation to the rest of the handle, corresponding to an adjustment of the grip in relation to the working position. Such adjustment is not detected by sensors, and does not result in any force feedback.
Another example from Immersion Corp. is the Laparoscopic Surgical Workstation, (LSW). Just as in the VLI, the shaft will rotate when the handle is rotated, requiring detection of rotation in the pivoting point. However, in this case it is the grip portion that is fixedly attached to the shaft. In order to enable adjustment of the grip position, a rotatable sleeve is arranged in front of the grip portion, and rotation of this sleeve relative the handle is detected separately. Moving the grip (and the entire handle) in relation to the sleeve will thus rotate the shaft, but the relative rotation between grip and sleeve will be detected, so that the simulation software can interpret this as a grip adjustment rather than actual instrument rotation. Grip action is detected in the grip portion similar to the VLI. The LSW is a haptic device, i.e. it has actuators arranged to provide force feedback in all degrees of freedom. In terms of force feedback, rotating only the sleeve (which does not rotate the shaft) and rotating the entire handle (including the sleeve and the shaft) will result in the same force feedback.
Yet another example is the Laparoscopic Impulse Engine (LIE), also from Immersion Corp. In this example, the shaft has a rotationally fixed exterior tube which does not rotate. Instead, the handle rotates in relation to the tube, and this motion is transferred by an axle extending inside the tube to the distal end of the shaft, where it is detected by a rotation encoder. Detection of grip action is done similar to the LSW mentioned above, by a sensor provided on the upper side of the grip portion. The LIE therefore also requires two signal interfaces on the moving parts of the device, one in the distal end of the shaft, and one on the grip portion. Each of these interfaces needs to be connected to the frame with a cord.
A relevant patent documents in this context are U.S. Pat. No. 6,323,837 and U.S. Pat. No. 6,902,405.
Despite the many user interfaces that are already available, these solutions are mechanically and electrically complex, typically with electric circuitry distributed between several locations. Also, they fail to correctly mimic an actual surgical instrument, such as a laparoscope, due to multiple cables connected to the device, and in some cases cables connected to the grip portion.